Microorganisms generally live attached to surfaces in many natural, industrial, and medical environments, encapsulated by extracellular substances including biopolymers and macromolecules. The resulting layer of slime encapsulated microorganism is termed a biofilm.
Biofilms are the predominant mode of growth of bacteria in the natural environment, and bacteria growing in biofilms exhibit distinct physiological properties. Compared to their planktonically grown counterparts, the bacteria in a biofilm are more resistant to antibiotics, UV irradiation, detergents and the host immune response.
It has for many years been a known problem to remove patches of underarm sweat from shirts and blouses. This stain is very difficult to dissolve and usually consists of a lot of different components. When laundry items like T-shirts or sportswear are used, they are exposed to bacteria from the body of the user and from the rest of the environment in which they are used. Some of these bacteria are capable of adhering to the laundry item and form a biofilm on the item. The presence of bacteria implies that the laundry items become sticky and therefore soil adheres to the sticky areas. This soil has shown difficult to remove by commercially available detergent compositions. Further, when very dirty laundry items are washed together with less dirty laundry items the dirt present in the wash liquor tend to stick to the biofilm. As a result hereof the laundry item is more “soiled” after wash than before wash.
Temperature has a significant influence on dissolving and wiping the components of sweat stain. Inadequate sweat stain removal can lead to discoloration of the area under the arms. This discoloration increases if the laundry is washed with other very dirty clothes. Sportswear is a good example because there is often soil, clay and traffic dirt on the clothes washed together with very sweaty shirts. From wash to wash the sweat stain become more and more colored so they eventually appear as developed spots. This kind of dirt is one reason why people discard their clothes. Although the problem is well known to most garment the problem is very pronounced for mixed fabrics. There is a European political desire to conserve resources for laundry which has led to their adoption of a labeling law for washing machines in the EU to exclude machines with high demand. This means that cold water washing is much more prevalent in the EU and thus come to resemble the rest of the world wash circumstances better. This means that there is a risk that energy consumption moves from wash warm and remove more sweat stain versus discarding clothes and buying new. There is an urgent need to solve the problem of removing sweat stains effectively.